This invention has to do with a method and apparatus for the cleaning of material handling conveyor belts and is especially concerned with an arrangement for cleaning continuous conveyor belts for the coal handling industry. It is a common problem with continuous conveyor belts that after the material has passed the intended delivery point it is sometimes carried backward on the underside of the looped belt due to moisture and other conditions that enable the material to stick to the conveyor belt. Such a condition is not desirable because of the dirty and dusty conditions created along the return side of the conveyor belt but also because of the damage that can be done to the support rollers on the underside of the moving conveyor belt.
Prior art devices that have attempted to solve the problem have included rotating brush assemblies mounted underneath and transverse to the direction of travel of the conveyor belt and spring mounted "doctor blade" assemblies as mentioned in U.S. Pat. No. 4,598,823.
The prior art devices all appear to involve mounting a brush or a blade on a transverse support bar that uniformly elevates or rotates so that all the brushes or blades become tensioned or move in response to the adjustment of the bar. The problem with many of the belts in service is that the loading of the material handled sometimes has a distribution that is heaviest in the middle of the belt and lightest on the sides of the belt. The uneven loading ha two effects on the conveyor belt. First the belt can take on a concave curvature that then becomes convex when the belt is viewed from the under side of the conveyor. Further, the belt can wear more in the middle than on the sides, causing it to be thinner in cross section in the middle. These two effects do not seem to be taken into consideration by the prior art devices because such devices call for adjusting the support bar in response to the above situation, which in turn moves all the blades or brushes attached to the bar the same amount or places the same tension on all the blades or brushes. Since the surface of the belt varies in location from the support bar due to the above conditions, the prior devices do not provide for an individual response by a single cleaning blade to the location of the surface of the belt it is intended to clean.
A further problem with the devices of the prior art is that in most cases the adjustment of the support bar must be accomplished manually at the end of the bar as it protrudes out from under the conveyor belt. In most cases this will not be a convenient area for a workman either because of the debris that may accumulate in the area or because the end of the belt is located in an inaccessible area.